Internet Explorer 9 has been downloaded 15 million times by Windows 7 and Vista users since the beta was unveiled 10 weeks ago, Microsoft said.

IE9 was downloaded two million times in the first 48 hours it was available, and 13 million more times since then, although it still commands less than half of a percent of the worldwide market for web browsers. The 15 million downloads represent 0.38 percent of the world's total browser usage, and just a fraction of the 240 million or so Windows 7 users (IE9 is available only on Vista and Windows 7).

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Microsoft lost ground in the browser market in November, with all editions of Internet Explorer combined now claiming 58.3 percent of users, down from 59.2 percent in October, according to Net Applications.

Rival Google Chrome claimed most of IE's lost share, upping usage from 8.5 percent to 9.25 percent in just one month.

Despite Internet Explorer's continued slide in the browser market, Microsoft marketing director Roger Capriotti enthused optimism in a blog, noting the 15 million download milestone for IE9 as well as numbers that show enterprises moving from IE6 to IE8.

Business customers have resisted moving away from IE6 in many cases, even though the browser is well out of date and full of security holes. The reliance on IE6 to run specific applications may even be stalling upgrades from Windows XP to Windows 7.

Capriotti claimed progress on this front, saying commercial usage of IE6 is down to 10.3 percent, "an all-time low," and significantly lower than the overall IE6 market share of 13.66 percent.

"As we continued to dig deeper into the data, we were pleased to see that the IE6 usage patterns are consistent regardless of the number of seats in the organisation and independent of the host operating system," he said.

"Small to medium sized organisations lead the pack in moving off of IE6, but even the largest enterprises with over 50,000 seats show similar trends – just 12.1percent of web browsing in those organisations comes from IE6. While XP usage contributes to IE6 usage, the vast majority of commercial XP machines have already upgraded to IE7 or IE8. Less than 20 percent of web browsing on commercial XP machines comes from IE6."

Commercial usage of IE8, meanwhile, is up to 34.1 percent and, overall, "IE8 usage worldwide grew 0.74 percent in month of November," he said. IE's decline must therefore be attributed to users ditching IE6 and IE7 for competing browsers such as Google Chrome.

Firefox also lost share in November, dropping from 22.83 percent to 22.75 percent. The only major non-Google browser to pick up share across all versions was Apple's Safari, which moved from 5.36 percent to 5.55 percent.

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